1. Field
A method of bonding semiconductor devices and more particularly, a method of bonding conductive interconnecting structures formed on a first substrate to conductive interconnecting structures formed on second substrate.
2. Description of the Related Art
Increasingly complex electronic systems require increasingly denser structures of integrated circuits, passive components, and other discrete elements. Typical two-dimensional structures, where the elements are laid out on a printed circuit board or similar structure are beginning to not meet the size, weight, and performance requirements of advanced electronic systems. Hence, three-dimensional structures are being used to provide the needed levels of electronic circuit integration. These three-dimensional structures generally comprise multiple layers of devices along with multiple layers of interconnects to provide electrical connections between the devices.
One approach for providing interconnects in a multiple layer structure is to bond semiconductor devices formed on a substrate (e.g., a first substrate) to semiconductor devices from another substrate (e.g., a second substrate). Such bonding can continue for several layers expanding vertically. Bonding typically occurs between a dielectric layer formed on the first substrate to another dielectric layer formed on the second substrate. Conductive metalizations for the devices on the substrate are formed through the dielectric layer (e.g., through openings or vias created in the dielectric layer) on the substrate to interconnect to conductive metalizations for devices on the second substrate. Alternatively, bonding can occur between a conductive metalization layer formed on the first substrate and another conductive metalization layer formed on the second substrate.
One major issue with wafer bonding as mentioned above is fast diffusion of the conductive metalization layers. Another issue is that the conductive metalization layers oxidize after the bonding of the two wafers together. Oxidation and diffusion of the conductive metalization layers results in degraded line resistance, electromigration performance, line-line shorting through diffusion of the conductive metalization layers, and device reliability.